Abstract

An instrument for microscale electrical transport measurements in ultra-high vacuum is presented. The setup is constructed around collinear lithographically-created multi-point probes with a contact spacing down to 500 nm. Most commonly, twelve-point probes are used. These probes are approached to the surface via piezoelectric positioners. Standard four-point resistancemeasurements can be performed using any combination of contacts out of the twelve available. Current/voltage measurements are taken semi-automatically for a variety of the possible contact configurations, effectively emulating measurements with an equidistant four-point probe for a wide range of contact spacings. In this way, it is possible to distinguish between bulk-like and surface-like conduction. The paper describes the design of the instrument and the approach to data and error analysis. Application examples are given for epitaxial graphene on SiC and degenerately doped Bi2Se3.

Received 03 December 2012Accepted 09 February 2013Published online 05 March 2013

Acknowledgments:

We thank the Carlsberg foundation for the financial support of this project as well as Capres A/S for their support. We gratefully acknowledge discussions with Lauge Gammelgaard and Peter Bøggild. The Bi2Se3 sample used in this work was provided by Jianli Mi and Bo Brummerstedt Iversen, and the quasi free-standing monolayer graphene by Felix Fromm, Christian Raidel, and Thomas Seyller.